Temperature corrected transepithelial electrical resistance (TEER) measurement to quantify rapid changes in paracellular permeability.

Determining the transepithelial electrical resistance (TEER) is a widely used method to functionally analyze tight junction dynamics in cell culture models of physiological barriers. Changes in temperature are known to have strong effects on TEER and can pose problems during the process of TEER measurements in cell culture vessels, complicating comparisons of TEER data across different experiments and studies. Here, we set out to devise a strategy to obtain temperature-independent TEER values based on the physical correlation between parameters such as TEER, temperature, medium viscosity and pore size of the cell culture inserts. By measuring the impact of temperature and different electrode types on TEER measurements on Caco-2 and HPDE (normal human pancreatic ductal epithelium) monolayers, we were able to derive a mathematical method that is suitable for the correction of TEER values for temperature changes. Applying this method to raw TEER values yields temperature-corrected TEER (tcTEER) values. Validity of tcTEER was demonstrated by showing a direct correlation with permeability of monolayers as determined by flux of RITC dextran. Taken together, the mathematical solution presented here allows for a simple and accurate determination of paracellular permeability independent of temperature variation during the process of TEER recording.

[Coagulation and formation of malignant effusions]. / Die Rolle des Gerinnungssystems bei der Entstehung maligner Ergüsse.

Malignant effusions are a frequent problem for cancer patients. Due to the high resistance of tumor cells within these effusions, no effective treatment has been defined yet. Most patients exhibit additional phenomena related to hyper-coagulability such as elevated levels for d-dimers and prothrombin fragments f1.2; half of them suffer from manifest thrombosis or complications. We followed the hypothesis that the activated coagulation system contributes to the resistance of tumor cells and analyzed the effusions from cancer patients. The majority of isolated tumor cells aberrantly expressed PAR-1 thrombin receptors. In vitro pre-incubation of PAR-1 expressing human leukemia cells with thrombin resulted in a dose-dependent resistance to idarubicin. Within the effusions, we did not only find high concentrations of VEGF and tissue factor, but also all coagulation factors of the tissue factor pathway. Very high levels of prothrombin fragments f1.2 indicate constant thrombin generation. Upon the basis of these findings, we developed a multistep model elucidating the pathophysiological generation of malignant effusions, which might serve as a basis for further examinations.